The invention describes an article made of a flexible rubber and/or plastic as well as a process for making this article.
Many flexible articles that are untreated on the surface, particularly those made of plastic and rubber, have a relatively high degree of friction resistance in relation to human skin. This is why untreated rubber gloves, for example, are almost impossible to put on. In order to make it easier to put these gloves on, glove powder (e.g. starch powder, talcum, etc.) is conventionally deposited as a parting compound on the inside of the glove. The use of powder, though, is particularly problematic in the medical field because residual powder can lead to granule formation if it gets into open wounds. Another important application field for powder-free products is the electronics industry.
A classic method for making articles of rubber and in particular, gloves that are slippery in relation to human skin without the use of powder, involves surface chlorination. In this connection, the article is treated with aqueous, chlorine gas-containing mediums and is then washed. Primarily, this produces a favorable slipperiness in relation to dry human skin, but this surface chlorination synthetically alters the polymer structure and thus produces a distinct diminishing of the physical and chemical properties of the article (strength, tear elasticity, water swelling, storability, etc.). However, surface-treated gloves of this kind are also usually difficult to put on with wet hands.
Coating with hydrogels represents an alternative surface treatment. Some hydrogels of this kind have been known for a long time. For example, these are polyurethane, polyvinylpyrrolidone, polyhydroxyethylacrylate or polyhydroxymethacrylate, polyhydroxypropylacrylate or polyhydroxypropylmethacrylate, and are copolymers with one another or with acrylic acid or methacrylic acid, acrylic ester or methacrylic ester, or vinylpyridine.
A coating of this kind has been disclosed by U.S. Pat. No. 3,813,695, which describes a dipped rubber glove that is coated on the inside with a hydrogel polymer such as polyvinylpyrrolidone, polyhydroxyethacrylate or polyhydroxymethacrylate, polyhydroxypropylacrylate or polyhydroxypropylmethacrylate, and copolymers of these with one another or with acrylic acid or methacrylic acid. The preferred hydrogel polymer is a copolymer of 2-hydroxyethylmethacrylate with methacrylic acid or with 2-ethylhexylacrylate or a ternary copolymer of 2-hydroxyethylmethacrylate, methacrylic acid and 2-ethylhexylacrylate.
A known manufacturing process is disclosed by U.S. Pat. No. 4,482,577. This patent discloses the coating of a flexible, vulcanized surgical glove with a hydrophilic polymer, by means of which the depositing of powder on the inside of the glove can be omitted. The copolymer used in this instance is comprised of a mixture of 2-hydroxyethylmethacrylate and 2-ethylhexylacrylate.
Another process according to U.S. Pat. No. 4,100,309 discloses the depositing of a slippery. coating comprised of a polyurethane-polyvinylpyrrolidone complex. Normally with these products or processes, the hydropolymer is deposited on the product together with a hardener in dissolved form, then the solvent is removed by drying, wherein the polymer layer is hardened, thus forming a hydrogel coating.
Other known embodiments disclose the use of vinylidene halogenide lattices or vinyl halogenide lattices for producing a slip coating on rubber articles, e.g. U.S. Pat. No. 5,069,965, where the slippery quality is mostly achieved by means of polymers that contain chlorine.
DE 26 28 059-C and U.S. Pat. No. 4,082,862 disclose the use of diverse latex mixtures for producing a slip coating. In particular, mixtures comprised of at least two latex types are used in this connection, wherein a latex type with a high elasticity is used as a bonding agent and a latex type with a high degree of hardness or low elasticity is used to obtain a sufficient slipperiness. These recipes are usually more or less favorable compromises between slipperiness, sufficient film flexibility, and adhesion of the film to the rubber product. In particular, with the use of the slip coating in very flexible, highly elastic rubber articles, there are often problems in this connection to the effect that the slip coatings used either begin to detach from the foundation when stretched or do not have a satisfactory slipperiness in actual use.
In the process according to EP 0 681 912-A2, the slip coating is comprised of a copolymer latex, which is fixed to the carrier layer with the aid of a coagulation step. The latex is comprised of a copolymer that contains a significant portion of hydrophilic monomer components.
U.S. Pat. No. 4,143,109 describes another method for producing slipperiness in relation to skin with powder-free medical gloves made of natural latex. In this instance, bonded cornstarch particles or polyethylene particles are deposited in a carrier layer, wherein the carrier layer is thinner than the diameter of the particles and the particles protrude from the surface. The powder particles bonded in this manner produce a sufficient slipperiness of the glove interior. This embodiment for achieving slipperiness in relation to skin has problems when the product is stretched to a great degree, which is inevitable when putting on latex medical gloves: The surface-bonded particles detach easily and the powder-free nature is no longer assured.
All of the above-described powder-free articles can only be produced with satisfactory product properties only under the most precise adherence to the affiliated process requirements and material recipes. While a favorable slipperiness of the surfaces in relation to dry skin is usually achieved with ease, very often there are difficulties in the reproducibility with regard to wet slipperiness. In particular with thin-walled flexible articles, which must have favorable slipperiness even when stretched to a great degree, it often takes years of high-precision optimization on the part of the manufacturer, who usually has to adopt compromises with regard to diverse product properties. Despite the use of polymeric slip coating hydrogels, the surface is frequently lightly chlorinated. Other manufacturers, in spite of the polymer slip coatings, use additional small quantities of glove powder. Still other producers see themselves as confronted with constant fluctuations with regard to the wet slipperiness of their products.
The object of the current invention is to produce articles made of plastic and/or rubber, which have a favorable slipperiness in relation to human skin, particularly wet skin, and to develop a process which can be easily reproduced.
This is attained by an article made of a flexible rubber or plastic, such as a glove, a condom, or the like, which includes a surface section that contacts or rests against human skin, and which is provided with a slip coating in a section of the surface that is comprised of a polymeric material and has at least a partial area having repeating surface shape deviations that are recessed in relation to a raised, net-like structure, where the ratio of the average spacings between the shape deviations to their depth, in relation to the raised, net-like structure, is between 500:1 and 5:1 and the average roughness depth is between 0.5 and 100 xcexcm, preferably between 1 and 40 xcexcm. In this connection, it is advantageous that the flexible products with the raised net structure and the recessed faces and the slightly roughened surface constituted by this have a significantly better slipperiness than smooth slip coatings, primarily in relation to wet human skin. This is particularly true for wet slipperiness, which is often difficult to achieve. A further advantage of the current invention is that avoiding occlusive skin contact makes wearing the articles more comfortable, improves their ability to be taken off, and if necessary, significantly improves their absorption of sweat. It is also significant that as a result of the rigorous reduction of the contact area between skin and polymer, in many cases, a significantly improved skin compatibility can be expected. In addition, allergic reactions are reduced and there is no confined feeling after the product is put on. It is advantageous that the roughened surface morphology according to the invention can be produced without additional mechanical or chemical treatment, such as embossing or chlorinating processes, and can also be produced, for example without the addition of a parting compound, e.g. powder or silicone. As a result, a favorable slipperiness can also be achieved using less optimal slip coating polymers. When a roughened surface structure is maintained, a favorable slipperiness can be achieved in both the wet and dry states.
According to another aspect of the invention, the flexible article is characterized in that between 50 and 90%, preferably between 60 and 80%, of the partial area""s repeating surface shape deviations are recessed. This is also advantageous since the wealth of micro-cavities formed in this manner can considerably reduce the friction potential or the contact area between the article and human skin.
According to another aspect of the invention, the flexible article is characterized in that at least 50% of the shape deviations, according to a top view of the slip coating, are encompassed on all sides by the net-like structure. This assures that a large part of the slip coating is kept at a distance from the skin by the net-like structure, even when the article is being worn, in which state the article is slightly stretched or drawn taut, so that in spite of the roughening, on the one hand, the user does not get the feeling that the article is chafing his skin and on the other hand, the movement of the hand, for example of the fingers, is not hindered since the slip coating or the partial surface of the slip coating does not stick to the wet skin.
The flexible article gives the skin a comfortable feeling if the slip coating comprises at least one natural and/or synthetic latex, or if the slip coating comprises a latex mixture and is fixed to the surface of the carrier layer.
Favorable properties for the slip coating and a firm adhesion of it to the carrier layer are achieved according to another aspect of the invention if the slip coating material comprises polyurethane.
A favorable skin compatibility for articles is achieved according to another aspect of the invention where the slip coating material comprises polyacrylates and/or polymethacrylates and/or polysiloxanes or other comparable products.
According to yet another aspect of the invention, surface roughness that is caused by the corresponding secondary treatment through chemical and/or physical reactions can be easily produced where the slip coating comprises 0 to 30 wt. % polyurethane, 1 to 40 wt. % polyacrylate, 1 to 20 wt. % polysiloxane, and 0 to 40 wt. % filler. Such surface roughness may be produced where the filler material comprises pulverized or powdered materials such as chalk, lime, cornstarch, silicon dioxide, and/or gypsum.
According to yet another aspect of the current invention, the use of a polymeric material in a slip coating that contains water absorbing groups makes the flexible articles particularly comfortable properties for people who perspire a lot.
According to still another aspect of the invention, perspiration retention on the surface of the skin can be better controlled in the region of the roughened surfaces in the sections, since the glove can absorb a higher quantity of moisture, where the polymeric material of the slip coating comprises intensely hydrophilic groups, for example acrylic acid and/or methacrylic acid and/or an acrylate and/or a methacrylate.
According to another aspect of the invention, a favorable connection with the slip coating in the sections can be achieved where the slip coating material has high surface adhesion and preferably is not cross-linked.
According to yet another aspect of the invention, the wet slipperiness of the articles can be additionally improved where silicone is deposited onto the regions of the slip coating which have surface roughening.
According to still another aspect of the invention, uniform slip behavior of the article is achieved where silicone is deposited onto regions of the slip coating.
According to yet another aspect of the invention, a very thin coating of silicone that increases slipperiness while at the same time preventing adhesion of the recesses, is achieved where the silicone on the surface sections of the slip coating is between 0.05 and 3 g/m2, preferably 0.25 g/m2.
According to another aspect of the invention, a slip coating or coatings is or are deposited on the inner surface of a sleeve-like carrier layer. According to yet another aspect of the invention, the slip coating is or are deposited on the outer surface of the sleeve-like carrier layer. According to still another aspect of the invention, the average roughness depth is lower in sections having lower relative movement between the flexible article and the skin of the user. These features provide slipperiness and slip properties as well as a roughness that corresponds, for example, to the grasping of tools or articles used in the assembly field.
According to another aspect of the invention, it is advantageous where at least one layer of the carrier layer is comprised of a latex product, which contains a polymer, e.g. a natural and/or synthetic latex since it can be used to produce extremely thin and extremely elastic articles that are also very resilient.
According to yet another aspect of the invention, the quality of the flexible articles can be considerably improved where the slip coating is provided on a carrier layer comprised of at least one layer, which preferably is slightly cross-linked. According to still another aspect of the invention, the latex of the carrier layer is pre-cross-linked.
According to yet another aspect of the invention, the article has a high degree of elasticity and suppleness where the carrier layer comprises an aqueous solution of a coagulant, which contains calcium nitrate, polyethylene glycol, a water soluble silicone or chalk, and a pre-cross-linked natural latex mixture.
According to another aspect of the invention, to make the carrier layer resistant the carrier layer contains a pre-cross-linked synthetic latex, e.g. chloroprene latex, NBR latex, X-NBR latex, or SBR latex.
According to yet another aspect of the invention, the carrier layer is embodied in a sleeve-like article having an outer surface and an inner surface which can be used to adapt the roughness of the individual surfaces or sections to the various intended uses of the article. According to another aspect of the invention, at least one surface section is disposed on the inner surface of the article, particularly of the glove, to achieve the intended roughness. Moreover, according to another aspect of the invention, at least one surface section is disposed on the outer surface of an article, particularly of a glove, which achieves the intended roughness.
According to another aspect of the invention, chlorinating the carrier layer on its surface further improves the effect of the roughness in the region of the carrier layer, or it produces at least a partial improvement of the slip properties in those regions where there is no roughening. Further, the raised edge regions of the chlorinated surface deformations caused by the chlorination may protrude above the neighboring surface zones by a height of 0.5 to 10 xcexcm, preferably less than 1 xcexcm.
According to another aspect of the invention, the inner surface of the slip coating of the article is provided with at least one of a coating of silicone and a treatment with chlorine, to cause preferred grading of the roughness and of the slipperiness of the flexible article in its various regions.
According to yet another aspect of the invention, the flexible article may be a rubber glove. According to yet another aspect of the invention, the article may be a medical glove.
Universal adaptations of adhesion, grip security, or slipperiness and wet slipperiness are achieved, according to another aspect of the invention, where the slip coating is deposited on the inner surface of the rubber glove or the medical glove. Further, only a section of the slip coating may have shape deviations in the region of its surface. Moreover, the surfaces of the rubber gloves or the medical gloves that are oriented toward the palm of the hand, or the back of the hand, may be provided with a slip coating, and if need be, at least sections of this slip coating may be provided with the surface shape deviations. Further, an outer surface of the rubber or latex glove may be provided with shape deviations where the ratio of the spacings of adjacent shape deviations to their depth is between 100:1 and 5:1, and their average roughness depth is between 0.5 and 100 xcexcm, and preferably between 1 and 40 xcexcm. Moreover, sections of the outer surface of the rubber glove or the medical gloves according to the invention may be provided with a slip coating and have surface shape deviations, at least in the region of the slip coating.
The invention also includes a process for manufacturing a flexible article, in particular a glove, where a carrier layer is made of plastic and/or rubber, and at least one section of its surface that has a slip coating, which is provided with a roughness in the region of its surface remote from the carrier layer. Moreover, where the slip coating is applied to the carrier layer by means of dipping and is dried immediately afterward, preferably for 10 to 600 sec. by means of hot air, and then the slip coating is treated with water at a temperature between 40 and 100xc2x0 C., preferably between 60 and 80xc2x0 C., or is rinsed with the hot water so that afterwards, the water content of the slip coating is reduced by approx. 40 to 70%, preferably 50 to 60%, such that a slip coating in a section of the surface is comprised of a polymeric material with at least a partial area having repeating surface shape deviations that are recessed in relation to a raised, net-like structure. The individual, succeeding measures produce a distortion in the surface of the slip coating and therefore produce the sinking of the recesses, which represent the deviations in shape, in relation to the intermediary pieces of the net-like structure that remain at the original height, by means of which a higher wearing comfort is produced by the higher elasticity, primarily when moving the fingers, and the slipperiness of the article is additionally improved in relation to human skin, above all when it is wet. Furthermore, the roughenings produced during the manufacturing process do not absolutely require additional treatment such as a subsequent chlorination or the application of a parting compound or the like.
According to another aspect of the invention, the flexible article is exposed to infrared radiation immediately following the draining period after the rinsing of the article with the hot water, and this permits the roughened structure that appears during the course of the drying process on the top side of the slip face or the net-like structure of intermediary pieces, which protrude by the measure of between 0.5 xcexcm and 100 xcexcm above the deviations in shape that are sunk with the dehydration, to produce a support grid that is supported on the surface of the skin and reduces the contact area between the skin and the article, without producing an uncomfortable scratchy effect that is felt when the surface is too rough.
The high temperature of the emitting body that gives off the infrared radiation, such as stove tiles, which may have temperatures of between 350xc2x0 C. and 700xc2x0 C., permits rapid stabilization of the surface deformations without causing the net-like structure to be reformed.
According to another aspect of the invention, by exposing the article to infrared radiation for between 1 and 5 minutes, the chemical reaction is finished in the entire article, both in the carrier layer and in the slip coating, and a secure connection is produced between these layers.
According to yet another aspect of the invention, the sunken shape deviations produced by the dehydration are prevented from leveling out again as a result of a uniform distribution of for example, the gelatinous fluid over the coating before they are permanently fixed, where the draining period between the rinsing of the article with the hot water and the application of infrared radiation is between 10 and 180 seconds, preferably between 20 and 50 seconds. The flexible may also be subjected to hot air during the draining period.
A favorable adhesion between the carrier layer and the slip coating is achieved according to yet another aspect of the invention, when during the drying of the coagulation solution of the latex product and/or the slip coating, which is preferably carried out with hot air, the surface of the latex product and/or the slip coating is converted from a liquid state into the gelatinous or solid state. Such adhesion also may be achieved when the drying of the surface of the latex product and/or the slip coating is carried out at a temperature from 70 to 140xc2x0 C., preferably at a temperature from 90 to 110xc2x0 C. Further, the drying process of the latex product and the slip coating may take between 10 and 80 seconds, preferably between 15 and 60 seconds.
According to another aspect of the invention, rapid dehydration of the slip coating accompanied by a more pronounced sinking of the shape deviation in relation to the net-like structure is achieved where the temperature of the hot water for rinsing the slip coating is between 40 and 95xc2x0 C., preferably between 70 and 90xc2x0 C., and the treatment lasts for 15 sec. to 8 min., preferably 30 sec. to 4 min.
According to still another aspect of the invention, the use of a slip coating comprised of a dispersion containing at least one polymeric material, increases skin compatibility and simplifies the manufacture of shape deviations that are sunken in relation to the net-like structure.
According to another aspect of the invention, a composition of dispersion is comprised of a mixture containing 0 to 30 wt. % of a polyurethane dispersion, 1 to 40 wt. % of a polyacrylate dispersion, 1 to 20 wt. % of a polysiloxane dispersion, and 0 to 10 wt. % filler, and the remaining portion water, encourages the formation of the net-like structure and the recesses that constitute the shape deviations. Moreover, the filler may comprise powdered or pulverized materials such as chalk, lime, cornstarch, silicon dioxide, and/or gypsum. Further, the viscosity of the dispersion of the slip coating may be between 5 and 30 mPa.""s, preferably 7 to 11 mPa.""s.
According to still another aspect of the invention, the roughness is created by the form surfaces on the carrier layer, which can improve the production of roughness in the carrier layer and/or the slip coating or in sections of them. According to another aspect of the invention, the recesses are produced by the pressing-in of fine beads or by sandblasting can improve the roughness of the carrier layer and/or the slip coating, or in sections of them.
According to still another aspect of the invention, a slip coating, preferably comprising silicone, is deposited onto the roughened surfaces of the flexible article.
Finally, according to yet another aspect of the invention, the shape deviation of the outer surface of the glove, in particular of a rubber or latex glove, as a result of the depositing of the carrier material onto a form whose surface has shape deviations in which the ratio of the spacings of adjacent shape deviations to their depth is between 100:1 and 5:1, and the average roughness depth is between 0.5 and 100 xcexcm, preferably between 1 and 40 xcexcm, improves the handling of tools or machine parts or components, particularly if these gloves are used in the assembly of electronic components or clean room parts.